Multistage centrifugal compressor



4 Sheets-Sheet 1 Filed Nov. 15, 1946 RALPH M.WATSON INVENTOR.

IIIHL Dec. 11, 1951 R. M. WATSON 2,578,617

MULTISTAGE CENTRIFUGAL COMPRESSOR Filed Nov. 15, 1946 4 Sheets-Sheet 2 RALPH M; WAT s on Dec. 11, 1951 RALPH MJWATSON Dec. 11, 1951 WATSON 2,578,617

' MULTISTAGE CENTRIFUGAL COMPRESSOR 4 Sheets-Sheet 4 Filed Nov. 15, 1946 m 0 Q Wi l -II- lllll I Fl 6-. I5

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Patented Dec. 11, 1951 v 2,578,617 MULTISTAGE CENTRIFUGAL COMPRESSOR Ralph M. Watson, Bloomfield, N. J., assignor to Worthington Pump and Machinery Corporation, Harrison, N. J a corporation of Delaware Application November 15, 1946, Serial No. 710,070

11 Claims.

This invention relates to centrifugal compressors and an object of the present invention is to provide large turbo-compressors which embody maximum standardization of parts which will permit relatively low cost of manufacture and expedite delivery of such machines.

Most requirements for compressors of this type are individual to specific requirements, and it has been the practice heretofore't design, engineer and build each compressor to meet the particular requirements of its use, resulting in not only relatively high cost of manufacture but also in considerable time consumed in building and completing the compressor for delivery after receipt of the order for it.

An object of the present invention is to provide a centrifugal compressor for compressing compressible fluids which is composed of a series of separate casings, one for each stage of compression, which casings are mounted independently of each other and free of mechanical a'ttachment to adjacent stage casings, and each of which stage casings is supported, independently of other stage casings making up the complete compressor, by a circular flange normal to the shaft axis. The flanges are supported by a common cylindrical housing surrounding all .of the stage casings and serving both as a supporting frame and a fluid tight enclosure sealing the entire machine within it. Each of said casings includes a stage impeller, volute passages and a return passage for directing the fluid from one stage to the successivestage of the multi-stage compressor.

The separate mounting of the stage casings in the outer compressor housing provides a wide range of flexibility in assembling various numbers of stage units and of fixing pressures and capacities to meet the requirements of the particular installation in which a compressor is to be used, while permitting the units to be standardized for economical manufacture.

Another object of the present invention is the provision of a centrifugal compressor as specified wherein the separate mounting of the stage units will permit temperature expansion of each unit without interference with adjoining units or the development of temperature stresses in the machine. 7

Another object of the present invention is to provide a compressor as specified wherein the pressureswithin the housing .are. .controlled by clearance spaces, defined by'the unit stage cas-l ings and the housing, which clearance spaces are sealed one from' another and are located between the unit-stage casings on the suction side of each unit-stage casing and the discharge side ofthe preceding unit-stage casing. Each of these clearance spaces is open to the discharge pressure of the succeeding impeller, or somewhat less, so that the venting of the discharge pressure of each impeller into the surrounding clearance space within the housing insures that each unit-stage casing and diffuser is subjected to a pressure which progressively increases from the suction end of the compressor t the discharge end. The casing as a whole is therefore subjected to an average internal pressure intermediate between the suction pressure and discharge pressure of the entire compressor.

With these and other objects in view as may appear from the accompanying specification, the

invention consists of various features of construction and combination of parts, which will be first described in connection with the accom panying drawings, showing a centrifugal compressor of a preferred form embodying the invention, and the features forming the invention will be specifically pointed out'in the claims.

In the drawings:.

Figure 1 is a side elevation of the improved centrifugal compressor.

Figure 2 isv an end view of the improved centhe improved centrifugal compressor includes ahousing I which is cylindrical in shape, being of uniform diameter throughout its length. The housing I is split longitudinally in a horizontal plane normal to the axis of the housing. The upper half 2 and lower half 3 are connected by means of flanges 4 so that when the lower half 3' is anchored to a supporting base (not shown) by means of the anchoring feet 5, the upperhalf 2 may be removed without effecting any of the internal parts of the compressor, or the suction and discharge piping (not shown). The suction and discharge piping are connected to thesuction nozzle 6 and discharge nozzle 1 respectively,

both of which are attached to the lower half 3 of the casing I. The suction nozzle 6, and discharge nozzle 1 may however without departing from the spirit of the present invention be located on the housing in any other positions than those shown, as conditions of use and installation of the comnressormay dictate.

Each of the stage units of the centrifugal compressor includes a unit stage casing I substantially cylindrical in shape and split in the medial. line thereof to form two halves which when joined together form the casingjproviding passages enclosing an impeller II which communicates with twin volute diffuser passages I2 in turn communicating with a return passage is for conductin the fluid from the twin volute diffuser passages I2 back toward theaxisof the unitstage casing I0 and delivering the fluid intoa suction inlet passage I4 of a subsequent stage of the multi-stage compressor.

Theftwin' volute diffuser passages I2 expand radially, enlarge in cross sectional area from their'inlets to'theiroutlets into the passages I4, and-"eachdiffuser passage pro ressively wi ens axially as it passes circumferentially around the impeller, so that as cut by a meridian plane the.- diffuser" passages are stepped in axial width oneach convolution (as clearly'shown in Figures 6.to 1' inclusive of the drawings).

The twinvolute diffusion passages I 2 develop from points 180 apart, thus balancing any side thrustitending'to deflect the shaft 25. The dif fuser passages I2 decelerate the flow' velocity gradually and efiiciently by'maintaining continuous curvature of passage in the samedirection withoutreversal- The impellers II may be ofanyapprovedtvbe;

but are shown in the drawings as of the inte rally castshroudedtypewith backward curved vanes directing the discharging fluid at a relative velocity -more-nearly tangential than radial and onpositely to thedirection-of rotation of theimpellers l I.

Each of the unit-stage casings!!! has an annularflan e I 5.formed upon itslperimeter which is normal to the axis of the casing and engages in an annular groove I 6 formed in the'inner surface of the housin I to independently mount and supper teach unit-stage casin I9 within the housing I in proper relation to the adjacent unitstaee casings so as to form a complete operative multi-stage compressor as clearly shown in Fig ure 3 of the drawings. Each unit stage casing lnvis arranged-so that its return passa e I3 will discharge into the inlet passage I ll of the succeeding' stage of the-compressor, excepting only thefinal unit-stage casing. I3 of the-final or dischar e unit-stage casing de livers the fluid from its-twin volute diffuser into theaannular "discharge-space I 1 of the compressor; which spacea IT; delivers thezfluid to the dis charge-nozzle 1';

The unit stage casings Ill-being supported and mounted independently"ofeach other in the cylindrical housing or shell I by means of the annularfianges' I5 provide l clearance s aces I8 ing 'and the dischargeside wall of the preced- The clearance spacesing unit stage casing I I]. IB-are open to the approximate dischargepressure'of'the impellerat the suction side of which The return passage they are located as clearly shown in Figure 3 of the drawings, so that each unit-stage casing Ii] except the first stage is subjected to a pressure diiference corresponding to only one stage compression of the fluid; the first stage casing is subjected to a somewhat greater pressure difference.

The formation of the clearance spaces I8 as just-described divides the interior of the housing I into a series of independent spaces in which the pressures progressively increase from suction pressure of the compressor at one end to discharge pressure at the other end.

The separate mounting of the unit-stage casings ID in thehousing I gives a wide range of flexibility in assembling various numbers of stage casings and of fixing pressures generated by the compressor and its capacity to suit the requirements of a particular installation, while permitting the units to be standardized for economical manufacture. That is, the separate mounting of the unit-stage casings permits these unit-stage casings to be manufactured in quantity lots and the various units to be assembled, from stock, into a multi-stage compressor to meet the requirements of the individual installation in which it is to be used.

All of the unit-stagecasings II! in their cooperative positions are enclosed in the housing I which is fluid tight-being rendered so by the connection of the'horizontally split'cylindrical shellZI and the suction head-I9 and discharge head 29. The suctionxhead I9 and the discharge head 20are substantially conical in shape, as clearly shown in Figure 3 of the drawings and are attached to the ends of the horizontally split cylindrical shellZI inany suitable manner such as by bolting as shown at 22.

The suction head. I9 co-operates with the suction side of the unit-stage casing I9 forming the first stage of compression of thecompressor to provide an annular suction passage 23 which opens into the suctioninlet I4 of the first stage unit-stage casing In.

The discharge endhead 29 co-operates with the discharge side of theunit-stage casing I9 forming the last stage of compression of the compressor to provide the annular discharge passage II into which the return passage I3 of the last :stage unit-stage casing discharges.

The pressure in any one of the clearance spaces i3 and in the annular inlet passage 23 and annular discharge passage I1 is uniform around the circumference of the housing I with no distorting effect tending to deflect the housing I or the unit-stage casing I0 out of round.

The impellers I I are carried by a shaft 25. The shaft 25 is of relatively large diameter avoiding the need of internal bearings, without risk of lateral vibration. The bearings, indicated at 26, are exterior of the-housing head: covers. I9 and 29, where they can be properly lubricated and cooled. The outboard bearing .26 is completely enclosed and the only opening where-leakage might occur is at the inboard endof the'shaft where a suitable'labyrinth seal, indicated at 21, is provided. The pressure to which the seal 21' is exposed is the inlet pressure of the compressor.

The axial thrust of the shaft 25 is carried by a balancing drum'28 the outer side of which is exposed to inlet pressure of thecompressor in the chamber or-space;29 behind the balancing drum 28.

Fluid under inlet pressure of the compressor is delivered to the chamber or space 29 through a longitudinal passage 30, which has communication with the annular suction space 23, and with a passage 3| in the head 20, which passage 3| leads to the chamber or space 29 as clearly shown in Figure 3 of the drawings.

In order to make the housing I cylindrical and of simple manufacture, the impellers ll progressively increase somewhat in diameter from suction to discharge of the compressor. This leaves sufiicient space around the suction impeller It to accommodate a diffuser passage required by the greater volume of flow at the suction end of the compressor and less space around the discharge impeller where the compressed fluid requires less space, with the spaces around the intermediate impellers decreasing towards the discharge impeller progressively in proportion to the volume reduction of the fluid as it is compressedin the successive stages. Moreover the inlet impeller H must be axially wider than subsequent impellers due to the larger volume of fluid flow and the wider spacing of its shroud rings leaves less support for the centrifugal loads on the vanes of the impeller. Hence the suction impeller is reduced in diameter to keep the stresses within permissible values.

If the compressor is to be used in a refrigeration installation, or in any other installation where it is desired to bleed fluid, under a pressure greater than the suction pressure of the compressor, into the compressor, bleed inlets, as shown at 34 may be provided which open into any one or more of the clearance spaces l8 to provide inter-stage bleeding into the compressor, or inter-stage bleeding out of the compressor in installations where it is desired to use fluid at pressures below the final discharge pressure of the compressor.

It will be understood that the invention is not to be limited to the specific construction or arrangement of parts shown, but that these may be widely modified within the invention defined by the claims.

What is claimed is:

1. In a multi-stage centrifugal compressor, a series of unit-stage casings each including an impeller, a diffusion passage, and a return passage for delivering fluid to the suction of the succeeding unit-stage casing, a housing enclosing all of said unit-stage casings, annular flanges on the perimeter of said unit-stage casings, said housing provided with grooves receiving said flanges for connecting each unit-stage casing to said housing independently of the other unit stage casings, said unit casings and flanges arranged to form a clearance space between the suction side wall of one unit-stage casing and the discharge side wall of the preceding unit-stage casing, said clearance spaces being sealed from each other by said flanges, a passage connecting the clearance spaces with the discharge of the next succeeding impeller whereby each unit-stage casing will be subjected to a relatively small pressure difference.

2. In a multi-stage centrifugal compressor, a series of unit-stage casings each including an impeller, a diffusion passage, and a return passage for delivering fluid to the suction of the successive unit-stage casing, a housing enclosing all of said unit-stage casings, annular flanges on the perimeter, of said unit-stage casings, said housing provided with grooves receiving said flanges \for connecting each unit-stage casing to said housing independently of the other unit stage casings, said unit casings and flanges arranged to form a clearance space between the suction side wall of one unit-stage casing and the discharge side wall of the preceding unit-stage casing, said clearance spaces being sealed from each other by 'said flanges, a passage connecting the clearance spaces with the discharge of the next succeeding impeller whereby each unitstage casing other than the first and last will be subjected to a pressure difference corresponding to the pressure difference of only one stage compression of the fluid compressed, said housing being split horizontally, said cleaarnce spaces being annular.

3. In a multi-stage centrifugal compressor, a series of unit-stage casings each including an impeller, a diffusion passage, and a return passage for delivering fluid to the suction of the successive unit-stage casings, a housing enclosing all of said unit-stage casings, annular flanges on the perimeter of said unit-stage casings, said housing provided with grooves receiving said flanges for connecting each unit-stage casing to said housing independently of the other unit stage casings, said unit casings and flanges arranged to form a clearance space between the suction side wall of one unit-stage casing and the discharge side wall of the preceding unit-stage casing, said clearance spaces being sealed from each other by said flanges, a passage connecting the clearance spaces with the discharge of the next succeeding impeller whereby each unitstage casing other than the flrst and last will be subjected to a pressure difference corresponding to the pressure difierence of only one stage compression of the fluid compressed, the impellers of said unit-stage casings increasing in diameter to regulate the volumes occupied progressively by the impeller of the inlet unit-stage casing to the impeller of the outlet unit-stage casing of the compressor.

4. In a multi-stage centrifugal compressor, a series of unit-stage casings each including an impeller, a diffusion passage and a return passage for delivering fluid to the suction of the succeeding unit-stage casing, a housing enclosing all of said unit-stage casings, annular flanges on the perimeter of said unit-stage casings, said housing provided with grooves receiving said flanges for connecting each unit-stage casing to said housing independently of the other unit stage casings, said unit casings and flanges arranged to form a clearance space between the suction side wall of one unit-stage casing and the discharge side wall of the preceding unit-stage casing, said clearance spaces being sealed (from each other by said flanges, a passage connecting the clearance spaces with the discharge of the a next succeeding impeller whereby each unitstage casing other than thefirst and last will be subjected to a pressure difference corresponding to the pressure difierence of only one stage compression of the fluid compressed, the impellers ofsaid unit-stage casings increasing in diameter and decreasing in axial width to regulate the volumes occupied progressively by the impeller of the inlet unit-stage casing to the impeller of the outlet unit-stage casing of the compressor.

5. In a multi-stage centrifugal compressor, a series of unit-stage casings each including an impeller, a diffusion passage, and a return passage for delivering fluid to the suction of the succeed-. ing unit-stage casing a housing enclosing all of said unit-stage casings, annular flanges on the perimeter'of said unit-stage casings, said housing provided with grooves receiving said flanges for,connecting;each unit-stage, casing to said housing independently of. the other unit stage. casings, said unit casings and flanges arranged to.

form aclearance spacebetween the suction side wallof one unit-stage casing and -the discharge side wall of the preceding unit-stage casing, said clearance spaces being sealed from each other by said flanges, a passage connecting the clearance spaces with the discharge of the next succeeding impeller whereby each unit-stage casing other than the first and last will be subjected to a pressure diflerence corresponding to the pressure difference of only one stage compression of the fluid compressed, the impellers of said unitstagecasings decreasing in volumetric capacity.

progressively from the impeller of the inlet unitstage casing to the impeller of the outlet-stage casing of the compress-or.

6. In a multi-stage centrifugal compressor, a

series of unit-stage casings each including an impeller, a diffusion passage, and a return passage for delivering fluid to the suction of the succeeding unit-stage casing, a housing enclosing all of said unit-stage casings, annular flanges on the perimeter of said unit-stage casings, said housing provided with grooves receiving said flanges for connecting each unit-stage casing to said housing independently of the other unit stage casings, said unit casings and flanges arranged to form a clearance space between the suction side wall of one unit-stage casing and the discharge side wall of the preceding unitstage casing, said clearance spaces being sealed from each other by said flanges, a passage connecting the clearance spaces with the discharge of the next succeeding impeller whereby each unit-stage casing other than the first and last will be subjected to a pressure difference corresponding to the pressure difference of only one stage compression of the fluid compressed, the impellers of said unit-stage casings decreasing in volumetric capacity progressively from impeller of the iniet unit-stage casing to the impeller of the outlet-stage casing of the compressor, said housing being of uniform diameter throughout its length.

'7. In a multi-stage centrifugal compressor, a series of unit-stage casings each including an impeller, a diffusion passage, and a return passage for delivering fluid to the suction of the succeeding unit-stage casing, a housing enclosing allof said unit-stage casings, annular flanges on the perimeter of said unit-stage casings, said housing provided with grooves receiving said flanges for connecting each unit-stage casing to said housing independently of the other unit stage casings, said unit casings and flanges arranged to form a clearance space between the suction side wall of one unit-stage casing and the discharge side wall of the preceding unit-stage casing, said clearance spaces being sealed from each other by said flanges, a passage connecting the'clearance spaces with the discharge of the next succeeding impeller whereby each unitstage casing except the first will be subjected to a pressure difference not exceeding the pressure difference of only one stage compression of the fluid compressed, the diffusion passage of each of said unit-stage casings being in the form of twin-volutes which expand radially and enlarge in crosssectional area progressively asthey ex; tend-circumferentially around the impellerof the unit-stage casing.-

8. In amulti-stage-centrifugal compressor,- a series of unit-stage. casings each includin an impeller, a diffusion passage and a return passage for delivering fluid to the suction of the succeeding unit-stage casing, a housing enclosing all ofsaid unit-stage casings, annular flanges on the perimeter of said unit-stage casings, said housing provided with grooves receiving said flanges for connecting each unit-stage casing to said housing independently of the other unit stage casings, said unit casings and flanges arranged to form a clearance space between the suction side wall of one unit-stage casing and the discharge side Wall of the preceding unit-stage casing, said clearance spaces being sealed from each other by said flanges, a passage connecting the clearance spaces with the discharge of the next succeeding impeller whereby each unit-stage casing except the first will be subjected to a pressure difference not exceeding the pressure difference of only one stage compression of the fluid compressed, the diffusion passage of each of said unit-stage casings being in the form of twinvolutes which expand radially and enlarge in cross sectional area progressively as they extend circumferentially around the impeller of the unit-stage casing, the impellers of said unit-stage casings increasing in diameter to regulate the volumes occupied progressively by the impeller of the-inlet unit-stage casing to the impeller of the outlet unit-stage casing of the compressor.

9. In a multi-stage centrifugal compressor, a series of unit-stage casings each including an impeller, a diflusion passage and a return passage for delivering fluid to the suction of the succeeding unit-stage casing, a housing enclosing all of said unit-stage casings, annular flanges on the perimeter of said unit-stage casings, said housing provided with grooves receiving said flanges for connecting each unit-stage. casing to said housing independently of the other unit stage casings, the diffusion passageof each of said unit-stage casings being in-the form of twin volutes which expandradially and enlarge in cross-sectional area progressively as they extend circumferentially around the impeller.

10. In a multi-stage centrifugal compressor, a series of unit-stage casings each including an impeller, a diffusion passage and a return passage for delivering fluid to the suction of the succceding unit-stage'casing, a housing enclosing all of said unit-stage casings, annular flanges on the perimeter of said unit-stage casings, said housing provided with grooves receiving said flanges for connecting each unit-stage casing to said housing independently of the other unit stage casings, the diffusion passage of each of said unit-stage casings being in the form of twin volutes which expand radially and enlarge in cross-sectional area progressively as they extend circumferentially around the impeller, the impellers of said unit-stage casings increasing in diameter to regulatethe volumes occupied progressively by the impeller of the inlet unit-stage casing to theimpeller of the outlet unit-stage casing of the compressor.

11. In a multi-stage centrifugal compressor, a series of unit-stage casings each including'an impeller, a diffusion passageand a return passage for delivering fluid to the suction of the. succeeding unit-stage casing, a housing enclosing. all of said unit-stage casings, annular flanges on the perimeterof said unit-stage casings, said house ing provided with groovesreceiving said flanges for connecting each unit-stage casing. to said housing independently of theotherunit stage casings, the diffusion passage of each of said unit-stage casings being in the form of twin volutes which expand radially and enlarge in cross-sectional area progressively as they extend circumferentially around the impeller, the impellers of said unit-stage casings increasing in diameter and decreasing in axial width to regulate the volumes occupied progressively by the impeller of the inlet unit-stage casing to the impeller of the outlet unit-stage casing of the compressor.

RALPH M. WATSON.

REFERENCES CITED The following references are of record in the file of thls gpatent:

UNITED STATES PATENTS Number Number Name Date Akimoff Dec. 27, 1910 Graemiger Apr. 16, 1918 'Irumpler May 10, 1932 Abramson Oct. 6, 1936 Babb Nov. 27, 1945 Trumpler June 21, 1949 FOREIGN PATENTS Country Date Great Britain Dec. 9, 1915 Great Britain Oct. 14, 1921 Germany Sept. 22, 1908 

